Bug #14409015 MEMORY LEAK WHEN REFERENCING OUTER FIELD IN HAVING

When resolving outer fields, Item_field::fix_outer_fields()
creates new Item_refs for each execution of a prepared statement, so
these must be allocated in the runtime memroot. The memroot switching
before resolving JOIN::having causes these to be allocated in the
statement root, leaking memory for each PS execution.

sql/item.cc

@@ -6010,7 +6010,12 @@ bool Item_ref::fix_fields(THD *thd, Item **reference)
       if (from_field != not_found_field)
       {
         Item_field* fld;
-        if (!(fld= new Item_field(thd, last_checked_context, from_field)))
+        Query_arena backup, *arena;
+        arena= thd->activate_stmt_arena_if_needed(&backup);
+        fld= new Item_field(thd, last_checked_context, from_field);
+        if (arena)
+          thd->restore_active_arena(arena, &backup);
+        if (!fld)
           goto error;
         thd->change_item_tree(reference, fld);
         mark_as_dependent(thd, last_checked_context->select_lex,

sql/item_subselect.cc

@@ -1135,7 +1135,7 @@ Item_in_subselect::single_value_transformer(JOIN *join,
   }
   else
   {
-    Item *item= (Item*) select_lex->item_list.head();
+    Item *item= (Item*) select_lex->item_list.head()->real_item();
 
     if (select_lex->table_list.elements)
     {

sql/sql_select.cc

@@ -528,8 +528,6 @@ JOIN::prepare(Item ***rref_pointer_array,
   
   if (having)
   {
-    Query_arena backup, *arena;
-    arena= thd->activate_stmt_arena_if_needed(&backup);
     nesting_map save_allow_sum_func= thd->lex->allow_sum_func;
     thd->where="having clause";
     thd->lex->allow_sum_func|= 1 << select_lex_arg->nest_level;
@@ -539,8 +537,6 @@ JOIN::prepare(Item ***rref_pointer_array,
 			  having->check_cols(1)));
     select_lex->having_fix_field= 0;
     select_lex->having= having;
-    if (arena)
-      thd->restore_active_arena(arena, &backup);
 
     if (having_fix_rc || thd->is_error())
       DBUG_RETURN(-1);				/* purecov: inspected */